DENTIN SIALOPROTEIN (DSP) TRANSCRIPTS - DEVELOPMENTALLY-SUSTAINED EXPRESSION IN ODONTOBLASTS AND TRANSIENT EXPRESSION IN PRE-AMELOBLASTS

Dentin sialoprotein (DSP), a 53 kDa glycoprotein, is believed to be pr esent exclusively in dentin. Using rat and mouse digoxigenin labeled ( DIG)-DSP and S-35-DSP riboprobes, and in situ hybridization techniques , we have studied the presence of DSP mRNA at specific developmental s tages of dentinogenesis. In mouse and rat molars and incisors, DSP tra nscripts were localized in young odontoblasts associated with early st ages of predentin formation, as well as in mature odontoblasts, cells with cytoplasmic extensions embedded in the forming dentin. No DSP tra nscripts were detected in dental pulp, enamel organ, ameloblasts, epit helial root sheath, Meckel's cartilage, alveolar bone or tibia. Furthe rmore, no DSP mRNA was observed in other soft tissues including heart, lung, kidney, intestine, eye, and muscle. In addition to the intense and prolonged expression by odontoblasts, DSP mRNA was transiently exp ressed by pre-ameloblasts in both developing molars and incisors. Thes e observations are consistent with the results of previous immunohisto chemical studies (1). The transient expression of DSP in pre-ameloblas ts across from young odontoblasts suggests an involvement of DSP in ep ithelial-mesenchymal interactions that are crucial to later stages of tooth development.